1. Field of the Invention
The present invention is broadly concerned with aqueous stable glycerin iodine concentrate products which can be diluted with water to form germicidal use solutions. More particularly, the invention pertains to such concentrates which have a high content of glycerin above 30% by weight, iodine, iodide ion and additive(s) (e.g., surfactants, hydrotropes, thickening agents, additional emollients, and/or buffering systems) which upon dilution yield high quality germicidal solutions with elevated free iodine values.
2. Description of the Prior Art
Iodine solutions have been used as germicidal agents for many years. In order to create useful solutions of this type, it is necessary to solubilize the iodine therein. Different solubilization approaches have been used in the past. These include hot processes wherein iodine is reacted with ethylene glycol or nonionic surfactants so that the resulting mixture is soluble in water, and room temperature solubilization using polyoxyethylene nonionic surfactants, polyvinylpyrrolidone or iodide ion. All of these solubilizing agents form a complex with the iodine, which in turn yields solutions (generally referred to as iodophores) which are used without further dilution and have varying concentrations of free or uncomplexed iodine (I.sub.2). Free iodine is a critical factor in determining the germicidal effectiveness of such iodine solutions, and therefore control of the free iodine level is very desirable if not essential.
It is known that the stability of aqueous iodine use solutions may depend upon the level of free iodine therein. However, high concentrations of free iodine corresponds to high levels of iodine vapor. In open containers, the iodine vapor will eventually cause a depletion of iodine from the solution. In plastic containers the iodine tends to dissolve into and eventually penetrate the container. Given that use solutions with a high free iodine value are generally more effective germicides, it would therefore be desirable to formulate a product having a low free iodine value during storage but which at the time of use could be adjusted to have a high free iodine value.
Many use solution iodophores designed for topical application are formulated with emollient in order to provide a soothing, skin-protective effect. In addition, most emollients will complex with free iodine thus assisting in adjustment and control of the free iodine content of the iodophore. The most common emollient used in such cases is glycerin, and may be present at a level of from about 1-15% by weight in products such as teat dips. Glycerine iodine use formulations also normally include one or more additives which are necessary to give the final use solutions desired physical properties. For example, surfactants are often used to provide wetting properties to insure complete contact between the surface to be disinfected and the use solution. Hydrotropes are also used to aid in the addition of other ingredients and to insure stability of the use solution. Buffering systems and thickening agents are also sometimes employed.
In recent years, manufacturers have sought to develop germicidal concentrate products which can be diluted with water at the point of use. Concentrates reduce manufacturing and freight costs, save storage space and minimize problem of disposing of containers. While certain types of iodophores can be readily formulated as dilutable concentrates, a significant problem arises when the concentrates contain appreciable amounts of glycerin and attendant additives such as surfactants, hydrotropes, additional emollients, buffering systems and thickeners. Specifically, high glycerin content iodophore concentrates tend to be unstable and rapidly separate into phases. This means that the end user must thoroughly mix the concentrate before dilution thereof. Such a requirement is not only inconvenient for the user, but can lead to use solutions having widely varying free iodine contents owing to inadequate mixing of the separated concentrate. As can be appreciated, if a given use solution has too high a free iodine content, it may be irritating; on the other hand, if the use solution has an inadequate free iodine content, its germicidal properties may be compromised.
To give but one example, a number of surfactants which are quite useful in the formulation of glycerin iodine diluted use solutions are incompatible when employed in the formulation of corresponding concentrates. Thus, polyoxyethylene alcohols, polyoxyethylene nonylphenol, polyalkylene block copolymers and polyvinylpyrrolidone are very difficult to use in concentrate formulations having high glycerin contents.
There is accordingly a need in the art for high glycerin content/low free iodine value iodophore concentrate products which have significant stability over long periods of storage, and which can be readily diluted with water to form use solutions having high, predictable and controlled free iodine contents.